Perfluorovinylethers are useful monomers for the manufacture of various fluoropolymers, in particular thermoprocessable tetrafluoroethylene-based plastics and fluoroelastomers.
Methods for manufacturing perfluorovinylethers from halofluoroethers are known in the art. Generally known methods involve dehalogenation of suitable halofluoroether precursors in liquid phase in the presence of transition metals.
For instance, US 2007203368 (SOLVAY SOLEXIS SPA) 30 Aug. 2007 discloses a liquid-phase process for the manufacture of perfluorovinylethers by dehalogenation of certain halofluoroethers in the presence of transition metals as zinc, copper, manganese or metal couples as Zn/Cu, Zn/Sn, Zn/Hg. Liquid phase processes generally suffer from the disadvantage that significant amounts of metal halides solutions or muds are typically obtained as by-products (e.g. ZnCl2 solutions/muds are produced when a chlorofluoroether is dechlorinated over zinc). Separation of said by-products from target perfluorovinylethers and their handling and disposal are time-consuming, costly and very burdensome from an industrial point of view, as these muds are highly corrosive and possibly endowed with negative environmental impact.
On the other hand, WO 2009/50091 (SOLVAY SOLEXIS SPA) 17 Dec. 2009 discloses a gas-phase process for the manufacture of a perfluorovinylether by hydrodehalogenation of a halofluoroether. Said process comprises contacting the halofluoroether with hydrogen in the presence of a catalyst comprising at least one transition metal of group VIII B at a temperature of at most 340° C. The process proceeds with high selectivity and without the formation of by-products which are difficult to handle.
Now the Applicant has surprisingly found that when the catalyst used in said gas-phase process comprises palladium and at least a second transition metal selected from group VIIIB and group IB metals the activity of the catalyst used in the hydrodehalogenation process may be retained for a longer period of time, thus increasing the economic profitability of the process.
The use of bimetallic catalysts in hydrodehalogenation reactions has been previously disclosed. For instance URBANO, F. J., et al. Hydrogenolysis of organohalogen compounds over palladium supported catalysts. J. Molecular Catalysis A: Chemical. 2001, vol. 173, p. 329-345. provides an overview of catalytic systems but it does not provide a specific disclosure of any catalyst compositions specifically suited for the hydrodehalogenation of halofluoroethers.
US 20050038302 A (HEDRICK ET AL.) 17 Feb. 2005 and EP 793633 B (SOLVAY SA) 17 Mar. 1999 similarly do not provide any teaching relating to the hydrodehalogenation of halofluoroethers.